Solvent-Free Stereoselective Synthesis of (E)-Trifluoromethyl Imines and Hydrazones

Abstract

A new, green and efficient strategy for the synthesis of trifluoromethyl ketimines, aldimines, and hydrazones starting from the corresponding trifluoromethyl carbonyl compounds or their hemiacetals is reported. The condensation reactions were performed under solvent-free conditions with a range of amines or hydrazines and proceeded with high stereoselectivity, always giving only the E-isomer in very good yields.

Key words

fluorinated compounds - imines - hydrazones - stereo­selectivity - condensation

References

• 1 Fluorine in Medicinal Chemistry and Chemical Biology   Ojima I. Wiley; Chichester: 2009. 
• 2 Prakash GKS. Paknia F. Vaghoo H. Rasul G. Mathew T. Olah GA. J. Org. Chem.  2010,  75:  2219 
• 3 Begue J.-P. Bonnet-Delpon D. Crousse B. Legros J. Chem. Soc. Rev.  2005,  34:  562 
• 4 Török B. Abid M. London G. Esquibel J. Török M. Mhadgut SC. Yan P. Prakash GKS. Angew. Chem. Int. Ed.  2005,  44:  3086 
• 5a Creary X. J. Org. Chem.  1987,  52:  5026 
• 5b Gosselin F. O’Shea PD. Roy S. Reamer RA. Chen C.-Y. Volante RP. Org. Lett.  2005,  7:  355 
• 6a Barney CL. Huber EW. McCarthy JR. Tetrahedron Lett.  1990,  31:  5547 
• 6b Gulevich AV. Shevchenko NE. Balenkova ES. Röschenthaler G.-V. Nenajdenko VG. Tetrahedron  2008,  64:  11706 ; and references therein
• 7 Abid M. Savolainen M. Landge S. Hu J. Prakash GKS. Olah GA. Török B. J. Fluorine Chem.  2007,  128:  587 
• 8a Fioravanti S. Pellacani L. Ramadori F. Tardella PA. Tetrahedron Lett.  2007,  48:  7821 
• 8b Colantoni D. Fioravanti S. Pellacani L. Tardella PA. J. Org. Chem.  2006,  71:  6295 
• 8c Colantoni D. Fioravanti S. Pellacani L. Tardella PA. Org. Lett.  2004,  6:  197 
• 9 Fioravanti S. Pellacani L. Tardella PA. Vergari MC. Org. Lett.  2008,  10:  1449 
• 10 Gong Y. Kato K. J. Fluorine Chem.  2001,  108:  83 
• 11a Molteni M. Volonterio A. Zanda M. Org. Lett.  2003,  5:  3887 
• 11b Iwata S. Ishiguro Y. Utsugi M. Mitsuhashi K. Tanaka K. Bull. Chem. Soc. Jpn.  1993,  66:  2432 
• 12 Soloshonok VA. Yasumoto M. J. Fluorine Chem.  2007,  128:  170 ; and references therein
• 13 Soloshonok VA. Ono T. J. Org. Chem.  1997,  62:  3030 
• 14 Crousse B. Bonnet-Delpon D. In e-EROS: Encyclopedia of Reagents for Organic Synthesis   Wiley; New York: 2005. DOI: 10.1002/047084289X.rn00560
• 15a Fuchigami T. Nakagawa Y. Nonaka T. Tetrahedron Lett.  1986,  27:  3869 
• 15b Neugebauer FA. Umminger I. Chem. Ber.  1982,  115:  3706 
• 15c Tanaka K. Maeno S. Mitsuhashi K. Chem. Lett.  1982,  543 
• 16a Funabiki K. Nagamori M. Matsui M. Enders D. Synthesis  2002,  2585 
• 16b Enders D. Funabiki K. Org. Lett.  2001,  3:  1575 
• 17 Yeh HJC. Ziffer H. Jerina DM. Boyd DR. J. Am. Chem. Soc.  1973,  95:  2741 
• 18 Kanai M. Ueda MKK. Yasumoto M. Kuriyama Y. Inomiya K. Ootsuka T. Katsuhara Y. Higashiyama K. Ishii A. J. Fluorine Chem.  2005,  126:  377 
• 19 Ros A. Díez E. Marqués-López E. Martín-Zamora E. Vázquez J. Iglesias-Sigüenza J. Pappalardo RR. Álvarez E. Lassaletta JM. Fernández R. Tetrahedron: Asymmetry  2008,  19:  998 
• 20a Tanaka K. Maeno S. Mitsuhashi K. J. Heterocycl. Chem.  1985,  22:  565 
• 20b Hegarty AF. Cashman MP. Scott FL. J. Chem. Soc., Perkin Trans. 2  1972,  1381 
• 22 Zhang W. Green Chem.  2009,  11:  911 
• 23 An efficient, although not stereoselective, synthesis of α-fluoroimines was very recently reported starting from α-fluoroketones, see: Malamakal RM. Hess WR. Davis TA. Org. Lett.  2010,  12:  2186 

21

The synthesis of 19 under solvent-free conditions gave the expected product in very low yields, probably because
p-nitrophenylhydrazine is a solid compound.